Mechanics mark scheme

Question 1

State what is meant by the centre of mass.

Answer 1

he point through which (the line of action of) a force has no turning effect/causes no rotation/ no torque ✔
OR
where the mass of the body can be considered to be concentrated OR where the weight can be considered to act ✔

Question 2

Explain why the centre of mass of the beam in the diagram must be vertically below A.

Answer 2

so there is not a resultant moment/turning effect / turning force OR moments do not balance OR (beam) does not rotate / oscillate / swing ✔
about A / because A is pivot ✔

Question 3

State two necessary conditions for the beam to be in equilibrium.
Condition 1 _________________________________________________________
___________________________________________________________________
___________________________________________________________________
Condition 2 _________________________________________________________

Answer 3

resultant/overall/sum of force = 0 OR forces up equal forces down AND forces left equal forces right ✔
(sum of) anticlockwise moments (about any point) = (sum of) clockwise moments/zero resultant moment/torque ✔

Question 4

State the quantity that is not conserved in an inelastic collision.

Answer 4

(Total) kinetic energy ✔